SACRAMENTO — Among the lesser-known provisions of the federal No Child Left Behind Act is a requirement that each state devise a system for determining whether a public school should be considered dangerous because of on-campus violence. Under the law, states get to decide what defines a “persistently dangerous” school, and parents whose children attend such a school can demand a transfer.

In California, the bar has been set so high even the roughest public schools come nowhere near meeting the state’s definition for dangerous, according to a recent federal audit.

In fact, since the 2002 federal law went into effect, not one of California’s 9,000-plus public schools has been labeled “persistently dangerous.”

That means many parents are given the false impression that nothing is wrong at their children’s schools, some safety officials say.

“When states tell the public, parents and the community that there are no persistently dangerous schools, it appears to be a stamp of approval,” said Kenneth Trump, president of the Ohio-based National School Safety and Security Services.

Writing in late March, federal auditors said that while the state’s policy meets the letter of the law, it “may not have met the intent of the (No Child Left Behind) Act, which was to provide parents with the knowledge and options to ensure that their children are attending a safe public elementary or secondary school.”

California ties its definition to a school’s expulsion rate. To be tagged “persistently dangerous,” a school would have to expel more than one out of every 100 students for three years in a row, and only expulsions that fall under nine serious categories count toward the label: inflicting serious physical injury, possessing or selling a firearm, brandishing a knife, assault on a school employee, robbery, sexual assault, selling drugs, possession of an explosive and hate crimes.

Those reasons for expulsion, while noted about 3,500 times by public schools statewide for the 2003-04 school year, are not cited by school administrators as frequently as many others, according to state Department of Education data.

Expulsions for violations such as possessing a knife, threatening someone or hitting a student but not causing serious injury don’t count toward the designation, though they happen more often. One reason for expulsion that is not counted toward the “persistently dangerous” label — “causing, attempting to cause, or threatening physical injury to another person” — was cited more than 5,200 times by schools statewide that year.

Like California, most states have policies in place that result in few schools getting labeled “persistently dangerous,” said Ronald Stephens of the National School Safety Center.

“Most states have created watermarks so high that few schools, if any, will ever rise to the level of an unsafe school,” Stephens said.

Supporters of California’s system say it is working just fine. The state’s standards are meant as a learning tool, not a punitive measure, said Matt Collier, an Elk Grove Unified School District administrator who was on the committee that helped devise the system.

The standards don’t unjustly punish schools that have a bad year or two, Collier added.

“I think you’ve got to look at it through a preventative type of lens,” he said. “The purpose is to allow schools that meet (the criteria for being labeled ‘persistently dangerous’) that first year to position more resources in place so they don’t meet them the second year.”